Thyroidectomy

Airway: ETT
Access: ~18G IV
Pain: Simple analgesia and PRN opioid usually adequate
Position: Supine with neck extended.
Time: 1-3 hours.
Blood loss: Low.
Special: Use of intraoperative nerve monitoring for laryngeal nerve preservation requires use of a specialised ETT, and absence of muscle relaxation.

Removal of thyroid gland, usually by transverse neck incision. Performed for:

Considerations

  • A
    • Goitre
      • Retrosternal
        • ⩾50% of goitres are retrosternal
          Associated with ↑ rate of complications.
        • 90% have airway issues
        • 1/3rd have dysphagia.
    • Anatomical distortion
      Difficult airway in 6%.
      • Tracheomalacia
      • Swallowing difficulty
        • Meat/bread
          Some sort of impingement.
        • Liquids
        • Secretion control
          Inability to control saliva/respiratory secretions indicates significant dysfunction.
      • Consider nasoendoscopy for baseline cord function
    • Airway plan
      Particularly afterwards. Plan for:
      • Minimising coughing
      • Recurrent laryngeal nerve palsy
      • Vocal change
    • Use of NIM tube
      ETT with built-in electrodes to monitor integrity of recurrent laryngeal nerves.
      • Surgeon identifies RLN with current of 0.2-2mA, which will stimulate cord movement
      • Cord movement generates an electrical signal in the tube which is read on the monitor
      • Reduce incidence of neuropraxia but not of long term RLN injury
        • Technical factors
        • ↑ external diameter of tube
          Minimum of 8.8mm OD.
        • Cannot be placed nasally
        • Requires stylet or FOI
        • Requires precise positioning; VL is helpful
          Electrodes must straddle cords.
        • Certain blocks will limit efficacy:
          • Nebulised lignocaine
          • Trans-tracheal lignocaine
          • Superior LN blocks
        • Avoid muscle relaxation during dissection
          Remifentanil, atracurium, or rocuronium/sugammadex for intubation.
  • B
    • Obesity
  • C
    • AF or CHF
      If hyperthyroid.
  • D
    • Use of nerve monitoring
  • E
    • Thyroid state
      Requires euthyroid state. Evaluate:
      • Normal T4/T3
      • Normal temperature
      • Normal HR, BP, pulse pressure
      • Normal reflexes
    • Electrolytes
      Notably hypocalcaemia.

Preparation

Induction

  • Standard induction
  • Shorter acting neuromuscular blockers should be used if using nerve integrity monitoring

Intraoperative

  • Ensure depth of anaesthesia adequate, particularly if incompletely treated hyperthyroidism

Surgical Stages

  • Skin incision
  • Platsyma divided
  • Subplatysmal flaps developed
    • Anterior jugular veins avoided
  • Prethyroid fascia divided in midline
  • Thyroid gland resected
    Depends on diagnosis.
    • Total
    • Subtotal
      Lobe, isthmus, +/- part of remaining lobe.
    • Lobar
  • Identification and preservation of the:
    • Parathyroid glands
    • Recurrent laryngeal nerve(s)
  • Excision of lymph nodes

Postoperative

Immediate serious post-operative complications include:

  • Recurrent laryngeal nerve damage
    • Bilateral
      Vocal cords adducted.
      • Unable to speak
      • Requires reintubation
        CPAP may temporise by splinting open cords.
    • Unilateral
      3-4%; hoarse voice.
  • Tracheomalacia
    Acute upper airway obstruction due to tracheal collapse.
    • Requires emergent reintubation or tracheostomy
    • Largely a historical remnant
      Risk is exceedingly rare in modern practice.
    • Suggested by no cuff leak prior to extubation
    • Risks may include:
      • Duration of goitre
      • Retrosternal extension of goitre
      • Significance of extrinsic compression
        Tumour; may also include bronchogenic carcinoma or aortic aneurysm.
  • Haematoma/Oedema
    Occurs in 1-2%, and expansion may lead to airway compromise.
    • Rapidly reopen incision and drain remaining blood
    • Consider CPAP to temporise airway
    • Reintubation may be required immediately, or delayed (on return to theatre)

Delayed complications include:

  • Hypoparathyroidism
    Inadvertent removal of parathyroid glands leading to acute fall in PTH and hypocalcaemia:
    • Occurs in ~20% of patients, with 3.1% being permanent
    • Presents as:
      • Laryngeal stridor
      • Tingling/numbness
      • Tetany
      • Seizures
    • Treated with calcium supplementation
      e.g. 10mL calcium gluconate IV.

References

  1. Findlay, J.M., G.P. Sadler, H. Bridge, and R. Mihai. ‘Post-Thyroidectomy Tracheomalacia: Minimal Risk despite Significant Tracheal Compression’. British Journal of Anaesthesia 106, no. 6 (June 2011): 903–6. https://doi.org/10.1093/bja/aer062.
  2. Atlas G, Lee M. The neural integrity monitor electromyogram tracheal tube: Anesthetic considerations. J Anaesthesiol Clin Pharmacol. 2013;29(3):403-404. doi:10.4103/0970-9185.117052